Since the invention of the transmission electron microscope (TEM) in 1930s (1932), especially for the past 20 years, significant progress has been made in TEM technology. With newly developed resolution enhancement technologies, such as spherical aberration (Cs) correctors for spatial resolution, monochromators for energy resolution, and high-speed CCD camera for time resolution, the modern TEM can be used to characterize a structure down to atomic scale, thus making great contributions to scientific progress in physics, chemistry, biology, materials science, and electronic information technology, etc. Meanwhile, as a current trend in TEM development, in-situ outfield measurement has been attracted increasing attention since it provides physical images for in-depth scientific studies. Direct observation of changes in microstructures of materials at atomic level provides the basis for fundamental understanding of physics, chemistry and materials science. However, due to the limitation of the current available technologies, research on the plastic deformation behavior of materials by TEM has been focused on the static material structures. It is often difficult to draw conclusions of certain findings due to the lack of knowledge on the dynamic evolution of microstructures.
The 654 and 671 type TEM sample holders produced by Gatan Company in America are the ones able to realize in-situ tensile test of sample under single tilt condition (around X axis), thus enables the real-time observation of reversible deformation twin in pure aluminum under TEM. Nanofactory Company in Sweden has developed in-situ deformation technology in TEM to study tension, compression and bending deformation as well as plastic deformation behaviors of nanowires. The PI 95 TEM picometer indenter manufactured by PI 95 Company in America can also be applied under single tilt condition (around X axis) to in-situ probe plastic deformation of various nanomaterials in TEM.
Although these commercial deformation devices in TEM provide a convenient tool for in-situ study of changes of microstructures during the deformation process of nanomaterials, information obtained is often limited. The existing commercial TEM sample holders used in in-situ mechanical behavior study normally only allow single tilting around X axis, so the tilting around Y axis cannot be realized. In addition, although the commercially available double tilt sample holder technology has been developed recently, these sample holders can only allow the observation of the sample; it is not feasible to simultaneously apply stress within the sample plane under double tilt condition. Thus the ability for in-situ study of mechanisms on the deformation, fracture, and phase change at atomic scale is significantly limited.
In particular, the above-mentioned methods apply stress on the samples by installing a complex mechanical device on the TEM sample holder. After installation of such device, the sample holder can only be used to apply stress on the sample under single tilt condition (around X axis), thus it is impossible to perform in-situ dynamic study on deformation mechanism under high-resolution state or at atomic scale, since the study also requires the application of stress while the sample is tilted around Y axis. Therefore, it poses great challenge for researcher in correctly understanding the performance of materials.